Coding and debugging external builds in Xcode

Create a new project, select "External build system" and specify the location in which to save the project files

Then add the source files with Project -> Add to Project…

Then add a new target with Project -> New Target…

Then delete the old target

Then double click on the new target and change any of the necessary settings including parameters for the make file and the path to the make file

Then add a custom executable with Project -> New Custom Executable… And set the full path to the executable including the file name

Now "Get Info" on the Project under the Groups & Files section.  Double click on "ARCHS" to change the architecture change "32" to "64" if necessary.

Then go to preferences and uncheck "Load symbols lazily" and that should be sufficient to build and debug an external project within Xcode.